genetics lecture 1

DNA

double-helix molecule holding biological instructions for building and running an organism

genes

specific segments of DNA coding for functional proteins or RNA, act as basic units of heredity

chromosomes

tightly wound thread-like packages of DNA located inside cell nuclei, humans have 46 (23 pairs)

alleles

diff variations of the same gene

genotype

organisms unique, underlying set of genetic instructions or alleles

phenotype

physical, observable traits created by interactions of genes + environment (ex- eye color)

chromatin

DNA combined with histone proteins

nucleosome

DNA coiled twice around core histones (H2A, H2B, H3. H4)

condensed DNA

chromosome, only fully condensed during cell division

decondensed DNA

chromatin, during interphase

euchromatin

loosely packed form of DNA, rich in active genes that allow it to be available for transcription

heterochromatin

tightly packed DNA, silences gene expression (ex- centromeres and telomeres)

centromeres

part of chromosome bound by proteins linking centromere to microtubules that transport proteins in cell division

telomeres

repetitive structures near ends of chromosomes, maintain length during replication

homologous chromosomes

pairs of similar but non-identical chromosomes, one pair comes from each parent (same genes, not same allele)

sister chromatids

two DNA molecules that form halves of a single, replicated chromosome (sequences usually identical, same versions of each gene)

plasmids

extra-chromosomal DNA molecules, not involved in genome, can carry genes, copied by cell and passed to daughter cells during cell division

ploidy

number of copies of each chromosome the organism typically has

haploid vs diploid vs aneuploid genomes

haploid- one copy of each chromosome

diploid- each chromosome represented in 2 copies/homologs (humans)

aneuplolid- cell or individual organism w extra or missing portion of genome

meiosis

formation of reproductive cells, have half number of copies of chromosome

karyotype

writte description of individuals set of chromosomes, written as 46, XY or when abnormality such as down syndrome 47, XY +21

karyogram

visual depiction of karyotype, image of chromosomes from single cell produced by images during metaphase

promoters

green lights, tell cell machinery where to begin reading gene

enhancers and silencers

act like volume knobs, turn up or down activity of specific genes

insulators

prevent gene from being accidentally turned on by neighboring gene’s control panel

telomeres

repetitive noncoding sequences, cap ends of chromosomes, protect genetic data from fraying when cells divide

centromeres

act as central anchors on chromosomes, help them line up and separate during cell division

epigenetics

study of how behaviors and environment cause changes that affect how genes work without changing your actual DNA sequence

histone modification

DNA wraps around spool-like proteins called histones, tight wrappng hides genes so they stay inactive and loose wrapping exposes DNA so transcription factors can turn genes active

DNA methylation

small chemical tags called methyl groups attach directly to DNA, typically silencing genes by blocking cellular machinery from reading them

epigenetic factors

development= epigenetic markers guide embryonic cells w identical DNA to specalize into entirely diff tissue types like skin, nerve, muscle cells

environment/lifestyle= diet, stress, activity, medication

health and disease= malfunctioning epigenetic tags can mistakenly turn off tumor-suppressing genes or activate stress and growth disorders

epigenetic inheritance

mechanism by which we pass acquired traits to our children, epigenetic changes to chromatin affect gene expression, 3 epigenetic marks: histone acetylation, histone methylation, and DNA methylation

writers

enzymes that add small chemical tags to DNA or histone tails, mark genome in response to environmental signals which can tightly pack DNA to silence it or loosen it to turn genes off

HATs, HMTs, DNMTs

readers

effector proteins w specialized domains that find and bind to specific chem tags placed by writers, translate chem marks into biological action, recruiting other proteins to alter chromatin structrure and activate/repress transcription

Methyl CpG

erasers

enzymes that remove chemical tags from DNA and histones, reverse work of writers

histone deactlylases and histon demthylases

histone tails

ends of histone polypeptides, stick out from core, pos charged amino acids lysine and arginine are over-represened